1. Field of the Invention
The present invention mainly relates to an absorbent article used in incontinence pads, sanitary napkins, panty liners, medical pads, toiletries, disposal diapers and the like, and an absorbent article including an absorbent body having a concave groove formed at a front surface thereof along a longitudinal direction thereof.
2. Description of the Related Art
In conventional absorbent articles, an absorbent body is provided between a liquid impermeable backsheet, such as a polyethylene sheet or a non-woven fabric made of laminated polyethylene sheets, and a liquid permeable topsheet, such as a non-woven fabric or a permeable plastic sheet.
This kind of absorbent article has been improved many times, and in particular, various products in which a concave groove is formed at a front surface in a longitudinal direction are provided, as temporarily reserving means and urine diffusing means for receiving a large amount of urine expelling at once by a small area and diffusing it immediately, such as incontinence pads (Patent Document 1 or the like, for example).
The applicant provides, in the previous patent application (following Patent Document 2), an absorbent article in which an absorbent body is provided between a liquid permeable topsheet and a backsheet, a concave groove substantially extending in a longitudinal direction is formed at a surface of the absorbent body at a liquid permeable topsheet side, and a highly compressed portion is formed at a bottom surface of the concave groove. The highly compressed portion is formed by a pattern in which a unit section, obtained by sectioning the concave groove in a longitudinal direction, is repeatedly positively inverted in the longitudinal direction of the groove, the highly compressed portion including an inclined element that is inclined with respect to a width direction of the groove and with respect to the longitudinal direction of the groove to substantially cross from a side end at one side to a side end at the other side of the concave groove in the unit section.
Patent Document 1: Japanese Patent No. 5,105,884
Patent Document 2: Japanese Patent Application No. 2013-229051
As the highly compressed portion with a predetermined pattern is provided at a bottom surface of the concave groove in the absorbent article disclosed in the above described Patent Document 2, effects can be obtained such as deformation of the concave groove when being worn can be prevented because the concave groove is reinforced by the highly compressed portion, and the body fluid can easily diffuse along the longitudinal direction of the groove as being induced by the highly compressed portion.
However, as exemplified as an example in the above described Patent Document 2 and illustrated in FIG. 10, if the pattern of the highly compressed portion provided at the bottom surface of the concave groove is formed by a wavy line that extends along the concave groove and repeats a concave portion and a protruding portion at both side in the width direction such that to reciprocate between the both side edges of the concave groove, there are following problems. As illustrated in FIG. 10 and FIG. 11-(A), when a user wears the absorbent article and pressure of legs by root portions of legs is applied from both sides in the width direction, at the protruding portion at which the highly compressed portion protrudes outwardly in the width direction, the protruding portion can function against the pressure of the legs that directs from outside to inside at the side where the protruding portion protrudes and the shape of the concave groove can be retained. However, for the pressure of the legs that directs from outside to inside at the side where the highly compressed portion is concaved, the opposite the above side, as the highly compressed portion that can function against the pressure of legs is not formed, there is a problem that the concave groove is easily collapsed and a space for retaining the body fluid becomes narrow (FIG. 11-(B)).
Further, as the highly compressed portion is provided at the bottom surface of the concave groove, as the liquid permeable topsheet is further drawn for an amount corresponding to the depth of the highly compressed portion, after being drawn for an amount corresponding to the depth of the concave groove, when providing the highly compressed portion, large compression distortion is generated in the front surface material. Thus, there is a risk that splits of the liquid permeable topsheet are generated in compression if a portion at which the direction of the groove drastically changes is provided in a plane pattern of the highly compressed portion. Further, if a fine pattern in which a plurality of closed pattern elements each being surrounded by the highly compressed portion are continuously formed along the concave groove, there are no escapeways for dispersing force applied in compression in the pattern elements. Thus, there are problems such as distortion by the compression is accumulated, splits of the liquid permeable topsheet are generated, an emboss roller is blocked because the liquid permeable topsheet is shaped in a shape of the pattern elements, and runnability is worsened. Further, if the highly compressed portion is formed by a fine pattern, as emboss protruding portions of the emboss roller are also formed by a fine pattern, runnability may be worsened because pulp paper powders are accumulated at cavities between such fine emboss protruding portions.